Introduction to heat exchangers
Before the process of selecting the correct heat exchanger is initiated it is of critical importance to form an understanding of the types of heat exchanger on the market and the merits/down sides to each of the aforementioned devices. This section of the report aims to provide a fundamental understanding of flow regimes and an introduction to various heat exchanger configurations.
In layman’s terms a heat exchanger is a device used to aid in the transfer of heat from one fluid medium to another. The fluids in question may be separated by a solid wall or may be free to mix as is the case in some applications. The surface area of the wall is maximised in a manner which tends to minimize disruption to the flow of the fluids. As is the case in some heat exchanger applications, fins or a form of corrugation may be used to induce turbulence and increase surface area.
Heat exchangers have a wide and varied list of applications in both an industrial and in a domestic sense, these applications range from a heat exchanger used in chemical processing to the fridge in your kitchen. Heat exchangers fall in to 3 flow arrangements (in which there is subdivisions due to the physical make-up of the product).The heat exchanger flow arrangements being; Counter flow, parallel flow and cross flow. “In the counter-flow exchanger, the fluids enter the exchanger from opposite sides. This is the most efficient design because it transfers the greatest amount of heat. In the parallel-flow version, the fluids come in from the same end and move parallel to each other as they flow to the other side. The cross-flow heat exchanger moves the fluids in a perpendicular fashion.” (Wisegeek.com, 2014).
Cross flow heat exchangers are...
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... has a satisfactory outcome.
With capital cost and overall efficiency being the most prevalent criterion when selecting heat exchangers, engineers or indeed members of the general public oft times purchase and commission heat exchangers with this narrow minded mind-set. The provision for future plant/process expansion and maintenance should be a paramount when selecting a heat exchanger. Any heat exchanger should facilitate easy maintenance, thusly increasing system performance and the product life cycle.
The old adage that you should over spec your heat exchanger bears merit in that it is nigh on impossible to recover from the short-comings associated with under-sizing a heat exchanger and an over specced heat exchanger allows for any increases in demand that may occur on a heat exchanger as well as compensating a degradation of HX performance over time.
Muller, S., Prowse, D. L., & Soper, M. E. (2012, September 25). CompTIA A+ Cert Guide: Power Supplies and System Cooling | Foundation Topics | Pearson IT Certification. Retrieved March 20, 2014, from http://www.pearsonitcertification.com/articles/article.aspx?p=1945640
The MCE is typically in the range of (1-5) k/T (in terms of the adiabatic temperature change). This modest change in temperature is obviously not sufficient for applications such as domestic refrigeration etc. [24].
A discussion on the HVAC heat loss calculations and miscellaneous supports. It was explained that the drawings showed an estimated tonnage, but the bidders were to size their units per their own calculations. The dual HVAC units as shown on the drawings represent N+1 redundancy as large VFDs are part of the building
Refrigeration, the production of cold, is an essential practice for present-day living. It is used in a many place like the processing and preservation of food, conditioning of air for comfort, manufacture of chemicals and other materials, cooling of concrete, medical applications etc. Refrigeration is defined as the science of maintaining the temperature of a particular space lower than its surrounding space. Refrigeration and air conditioning involves various processes such as compression, expansion, cooling, heating, humidification, de-humidification, air purification, air distribution etc. In all these processes, there is an exchange of mass, momentum and energy. All these exchanges are subject to certain fundamental laws. Hence to understand and analyses the refrigeration and air conditioning systems, a basic knowledge of the laws of thermodynamics, fluid mechanics and heat transfer is essential.
In order to study the aspects of fluid mechanics that need to be taken into account when constructing our cooling tower, a breakdown of different behaviours of fluids under different conditions must be performed and tested against the flow rate. The experimental design would have to explore the influence of the length of the flow pipe as well as the density and temperature on the flow rate of the fluid.
The simplified schematic diagram of the engine representing the heat exchanger and the pistons configuration of the system is as shown in figure 1 (Minassians & Sanders 2011). The gas circuit of the displacer subsystem is closed by means of tubing in order to provide a closed engine chamber. Both the displacer and the power piston have equal dimensions. In single-phase operation, the power piston interacts
Investigating Heat Loss From a Container Planning We are investigating heat loss from a container and how it is affected. We could change: Room temperature Surface area Amount of water Use a lid Insulate around it Colour of tin We could measure / observe: Amount of time Temperature We will change: Surface area We will measure / observe: Temperature (every minute for 5 minutes) Our question is: Does surface area effect the rate of heat loss? We will keep these the same: Colour of tin Room temperature Amount of water Use a lid Insulate around it Preliminary investigation = == ==
good emitter of heat radiation so a lot of heat will be lost to the
heat will stay in the cup and can only escape by rising to the surface
In this paper over natural refrigerant I will be covering the pros and cons of natural refrigerant in light commercial and residential applications. There are many natural substances in this world that can be used to help or decrease the efficiency of a heating ventilation air conditioning system. Some of these substances are water, air, ammonia, and hydrocarbons. All these substances are natural that come from the earth we live on. Over the course of this paper I will be covering the pros and cons of swamp coolers, geo thermal heating and cooling units and how these natural substances can help and or decrease how your heating and cooling unit performs.
In a slatted, counter-current cooling tower, warm water enters the top of the tower and flows down a series of slatted inserts inside of tower. An air source is introduced at the base of tower, which flows up the tower. As the air interacts with water flow on the slats, the temperature differences causes evaporation. Water’s change from a liquid to a gas phase requires a large amount of energy, approximately 2326 kJ/kg at atmospheric conditions, which provides a cooling effect to the water [3].
The factors for exponential growth for air-conditioning are the HVAC Market, energy, environment, communication, societal, political, preparing for the future, looking ahead, and the conclusion. Buildings of the U.S. use approximately 35% of the nation’s precise total of energy consumption. The worth of shipments by U.S. HVAC manufacturers was over $28 billion of 1996. Since there are 52,000 CHC chillers needed to be replaced among the U.S., there’s a large opportunity for new chillers, new technology for the HVAC industry. The ozone depletion is an international issue in which is currently being resolved. The 3rd world countries are still allowed to manufacture CFC’s. Illegal imports of CFC’S to the U.S. is a consistent concern. Many illegal imports are virgin CFC’s. Those whom have a political overtones are specifically the ones whom create a protectionism of local commerce, having a negative impact on those inside and out of the country.
These resources can be classified as low temperature (less than 194 degrees F), moderate temperature (194 – 302 degrees F), and also high temperature (greater than 302 degrees F). The uses to which these resources are applied are also influenced by temperature. If the reservoir is to be used for direct-heat application, the geothermal water is usually fed to a heat exchanger before being injected back into the earth. Heated domestic water from the output side of the heat exchanger is used for home heating, greenhouse heating, vegetable drying and a wide variety of other uses.
... temperature of 112 0C also and a pressure 2.5 bar. Cooling water is used to condense the vapor exiting column. Remaining methane and hydrogen are separated in reflux drum where the vapor stream is combined with other gases streams. The overhead of first and second separator are combined to form fuel gas. The liquid stream exiting in the bottoms of the reflux drum is pumped at pressure of 3.3 bar for discharging pressure. The pump stream is separated in two streams. One stream is to feed to tray one of the column and the other one stream is cooled down to 38 0C in heat exchanger. Then, the cooled product stream is sent to storage.
In thermodynamics Refrigeration is the major application area, in which the heat is transferred from a lower temperature region to a higher temperature region. The devices which produce refrigeration are known as Refrigerators and the cycle on which it operates are called refrigeration cycles. Vapour compression refrigeration cycle is the most regularly used refrigeration cycle in which the refrigerant is alternately vaporized and condensed and in the vapor phase it is compressed. Gas refrigeration cycle is the well-known refrigeration cycle in which cycle refrigerant remains in the gaseous phase throughout the cycle. Cascade refrigeration are the other refrigeration cycles discussed in this chapter; absorption refrigeration is the one more refrigeration cycle which is used where the refrigerant is dissolved in liquid before it is compressed. One more refrigeration in which refrigeration is produced by passing the electric current through two dissimilar materials is called as the thermoelectric refrigeration.